The metabolic syndrome is a constellation of interrelated risk factors of metabolic origin that appear to promote the development of atherosclerotic cardiovascular disease and increase risk for type 2 diabetes. Although powerful pharmacological treatments for some metabolic syndrome components exist, these treatments are not entirely effective and are often associated with serious side-effects. Therefore, there is considerable interest in finding alternative treatments for the metabolic syndrome components. The broad, long-term objectives of this research program are to find complementary and alternative treatments for the metabolic syndrome. Animal studies and observational data in humans suggest that supplemental melatonin may provide protection against a number of metabolic syndrome components, including elevated glucose, elevated blood pressure, dyslipidemia, and obesity. Evidence also suggests that individuals with metabolic syndrome components have suppressed melatonin levels, and hence may be particularly likely to benefit from exogenous melatonin supplementation. However, experimental data on the ability of melatonin supplementation to improve metabolic syndrome components are lacking. Accordingly, we propose to conduct a pilot randomized, double-blind, placebo-controlled crossover trial that will obtain preliminary data about the effects of melatonin supplementation on metabolic syndrome components in adult men and women with the metabolic syndrome. We hypothesize that melatonin supplementation will safely alleviate one or more of the metabolic syndrome components in these subjects. Thirty-six metabolic syndrome patients will be recruited into the study to address this hypothesis through the following specific aims: 1) To obtain preliminary data on the effect of melatonin on metabolic syndrome components in persons with metabolic syndrome. 2) To explore whether sleep, oxidative stress, and inflammation are potential mechanisms that mediate the effects of melatonin on metabolic syndrome. 3) To determine whether melatonin supplementation has any adverse side-effects when taken daily for 13 weeks in adults with the metabolic syndrome. 4) To determine the feasibility of recruiting and retaining a sufficient number of metabolic syndrome patients for a larger, more definitive study. Result obtained from the study will provide necessary information for a larger, more definitive study. PUBLIC HEALTH RELEVANCE: This project is relevant to public health because it will provide much needed data on the ability of melatonin supplements to ameliorate the metabolic syndrome, which is a major risk factor for cardiovascular disease and diabetes. This study will also provide much needed information on the safety of long-term melatonin use in metabolic syndrome patients.